Abstract:

The present invention provides an optical disc on which a visible image
can be formed by irradiation of laser light, which comprises a logo area
on which visible information is indicated, a pre-pit signal area, and an
image forming area on which a visible image can be formed by irradiation
of laser light; and an image forming method of forming a visible image by
irradiation of laser light on an optical disc, the method including
detecting a pre-pit signal from a pre-pit signal area formed on the
optical disc, and forming the visible image based on the result of the
detection, wherein the optical disc is the optical disc of an aspect of
the invention.

Claims:

1. An optical disc on which a visible image can be formed by irradiation
of laser light, which comprises:a logo area, on which visible information
is indicated;a pre-pit signal area; andan image forming area, on which a
visible image can be formed by irradiation of laser light.

2. The optical disc of claim 1, wherein the image forming area is
positioned at a deeper level than the logo area.

3. The optical disc of claim 2, wherein the pre-pit signal area is
positioned at a deeper level than the logo area.

4. The optical disc of claim 3, wherein an outer circumference of the logo
area is positioned closer to an outer circumference of the optical disc
than an inner circumference of the pre-pit signal area.

5. The optical disc of claim 1, wherein an image-recording layer of the
image forming area is formed between two substrates facing each other.

6. The optical disc of claim 5, wherein the two substrates each have a
thickness of 0.3 mm to 0.9 mm.

7. The optical disc of claim 5, wherein an indented portion is formed on
the substrate on which the image-recording layer is formed, at the side
having the image-recording layer, and the indented portion forms the logo
area.

8. The optical disc of claim 1, wherein the logo area comprises two or
more layers.

9. An image forming method of forming a visible image by irradiation of
laser light on an optical disc, the method comprising:detecting a pre-pit
signal from a pre-pit signal area formed on the optical disc; andforming
the visible image based on the result of the detection;wherein the
optical disc is the optical disc of claim 1.

10. The image forming method of claim 9, wherein in the forming of the
visible image, the laser wavelength is 630 nm to 680 nm and the numerical
aperture is 0.6 to 0.7.

Description:

TECHNICAL FIELD

[0001]The present invention relates to an optical disc on which an image
can be formed by laser light and a method of forming an image on optical
discs.

BACKGROUND ART

[0002]As optical discs such as a write-once digital versatile disc
(DVD-R), etc., optical discs having an ink receiving layer (printing
layer) on their labeling side (a side opposite to the side on which laser
light is irradiated during recording or reproduction of optical
information) are in use in practice. Users can print pictures or drawings
on the printing layer using an ink jet printer, etc.

[0003]Procedures for printing an image using an ink jet printer, etc. are
advancing day by day, and image quality obtained has become exceptional.
On the other hand, however, providing a new ink jet printer, etc., for
forming an image is costly. Furthermore, transferring an optical disc to
an ink jet printer, etc. to form an image thereon, after recording
information on the optical discs, takes time and effort. The task seems
to be more complicated where information is recorded on plural optical
discs and images are formed therefrom. Furthermore, when a printing layer
is provided on the surface of the optical disc, there is a fear that
problems of storability, such as deterioration due to moisture in the
air, stains due to adhesion of dusts, etc., may arise.

[0004]Image forming apparatuses and methods for forming an image that can
record an image having a high contrast ratio on an optical disc as well
as recording information on the recordable side have been suggested (for
example, see Japanese Patent Application Laid-Open (JP-A) No.
2004-005848). Furthermore, several optical recording media on which an
image can be formed by irradiation of laser light are known (for example,
see JP-A Nos. 2000-113516, 2001-283464 and 2000-173096). These are
convenient in that they can form good visible images. However, it is
impossible to recognize on which side of an optical disc an image can be
formed. Furthermore, quality control, etc. may become difficult since
these optical discs do not comprise supplemental information, such as
image forming information, etc.

[0005]Therefore, there is a need for an optical disc in which a side on
which image forming is carried out and a side on which image forming is
not carried out can be easily distinguished and quality control thereof
is easy Furthermore, there is a need for an image forming method, which
is suitable for image forming on such an optical disc.

DISCLOSURE OF INVENTION

[0006]According to an aspect of the invention, there is provided an
optical disc on which a visible image can be formed by irradiation of
laser light, which includes: a logo area, on which visible information is
indicated; a pre-pit signal area; and an image forming area, on which a
visible image can be formed by irradiation of laser light.

[0007]According to another aspect of the invention, there is provided an
image forming method of forming a visible image by irradiation of laser
light on an optical disc, the method including: detecting a pre-pit
signal from a pre-pit signal area formed on the optical disc; and forming
the visible image based on the result of the detection; wherein the
optical disc is the optical disc according to an aspect of the invention.

BRIEF DESCRIPTION OF DRAWINGS

[0008]FIGS. 1A and 1B are partial cross-sectional views showing examples
of the constitutions of the layers for the optical disc of the present
invention.

[0009]FIGS. 2A, 2B and 2C are top views showing examples of optical discs
of the invention.

[0010]FIGS. 3A, 3B and 3C are partial cross-sectional diagrams showing
examples of the optical discs of the invention.

[0011]FIG. 4 is a block diagram showing the structure of an example of an
optical disc recording apparatus that can use the optical disc of the
invention.

[0012]FIG. 5 is a diagram showing the structure of the optical pickup
which is a component of the optical disc recording apparatus.

[0013]FIG. 6 is a diagram which explains the content of the image data
used for the formation of a visible image on the image-recording layer of
the optical disc by the optical disc recording apparatus.

[0014]FIGS. 7A and 7B are diagrams explaining the laser irradiation
control for expressing the gradation of the image employed upon formation
of a visible image on the image-recording layer of the optical disc of
the invention by the optical disc recording apparatus.

[0015]FIGS. 8A and 8B are diagrams for explaining the laser beam control
method employed upon formation of a visible image on the image-recording
layer of the optical disc by the optical disc recording apparatus.

[0016]FIG. 9 is a diagram for explaining the laser power control performed
by a laser power controlling circuit that is a component of the optical
disc recording apparatus.

[0017]FIG. 10 is a diagram showing returning light of the laser beam
originally emitted by the optical pickup of the optical disc recording
apparatus to the image-recording layer of the optical disc.

[0018]FIG. 11 is a diagram showing an FG pulse generated by a frequency
generator 21 which is a component of the optical disc recording apparatus
based on the revolutions of a spindle motor, and a clock signal generated
based on the FG pulse.

[0019]FIG. 12 is a flowchart for explaining the operation of the optical
disc recording apparatus.

[0020]FIG. 13 is a flowchart for explaining the operation of the optical
disc recording apparatus.

[0021]FIG. 14 is a diagram showing a disc ID recorded on the
image-recording layer side of the optical disc.

[0022]FIG. 15 is a diagram showing shapes of the returning laser beams
that are received by the light-receiving element of the optical pickup of
the optical disc recording apparatus.

[0023]FIGS. 16A and 16B are diagrams for explaining the size of the beam
spot of a laser beam that the optical pickup of the optical disc
recording apparatus emits to the image-recording layer of the optical
disc.

[0024]FIG. 17 is a diagram for explaining a method for detecting that the
laser irradiation position of the optical disc recording apparatus has
passed the reference position on the optical disc.

[0025]FIG. 18 is a diagram for explaining a method for detecting that the
laser irradiation position of the optical disc recording apparatus has
passed the reference position on the optical disc.

[0026]FIG. 19 is a timing chart for explaining the operation of the
optical disc recording apparatus upon irradiation of the image-recording
layer of the optical disc with a laser beam to form a visible image.

[0027]FIG. 20 is a diagram showing the image-recording layer of the
optical disc at irradiation with a laser beam emitted by the optical disc
recording apparatus.

[0028]FIGS. 21A, 21B, 21C and 21D are top views showing examples of the
optical discs of the invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Optical Disc

[0029]The optical disc of the present invention is an optical disc on
which a visible image can be formed by irradiation of laser light, which
comprises a logo area on which visible information is indicated, a
pre-pit signal area, and an image forming area on which a visible image
can be formed by irradiation of laser light. By the visible information
indicated on the logo area, a side on which image forming is carried out
can be readily distinguished from a side on which image forming is not
carried out. Furthermore, quality control becomes easy due to the pre-pit
signal generated from the pre-pit signal area. Furthermore, since the
optical disc has an image forming area on which a visible image can be
formed by irradiation of laser light, a visible image having high
contrast can be formed efficiently.

[0030]As used herein, the visible information that is indicated on the
logo area refers to an indication for distinguishing a side on which a
visible image can be formed by laser light from a side on which an image
cannot be formed. Examples of the indication include letters such as
"DRAWABLE SIDE", "NON-DRAWABLE SIDE" and the like, and illustrations that
enable ready discrimination of whether letters or images can be formed or
not, and the indication is provided on the logo area so that, for
example, the indication can be recognized from either of the drawable
side or the information recording side (recordable side, which means a
side on which information can be recorded). For example, for the logo
area 702a of FIG. 2B, an indication "LABEL SIDE--DRAWABLE" is provided on
the label side, and for the logo area 702b of FIG. 2C, an indication
"DATA SIDE--NOT DRAWABLE" is provided on the recordable side.
Furthermore, as shown in FIGS. 21A, 21B, 21C and 21D, embodiments in
which an indication "DRAWABLE SIDE" is provided on the drawable side of
the optical disc (FIG. 21A) and an indication "NON-DRAWABLE SIDE" is
provided on the recordable side (rear side) (FIG. 21B) are also possible.
Alternatively, embodiments in which an indication "DRAWABLE SIDE" is
provided on the drawable side of an optical disc and no indication is
provided on the recordable side (rear side) (FIG. 21D) are also possible.

[0031]By using such indications showing that a side is drawable or that
drawing is prohibited, the insertion of an optical disc into a drive,
mistaking a side on which recording is prohibited for a recordable side
can be avoided when image recording. Namely, a side on which an image
forming can be carried out can be readily distinguished from a side on
which image forming cannot be carried out. It is preferable to provide
the logo area on the outermost surface of the label side, because
printing design can be readily changed while using the same specification
of the disc main body.

[0032]Examples of the methods for providing such visible information
include a method including providing a profiled surface corresponding to
the indication on the substrate, printing methods such as screen
printing, etc. The profiled surface can be provided on the substrate by
providing in advance a corresponding profile on the stamper for forming a
substrate, and forming the substrate using the stamper by injection
molding.

[0033]The pre-pit signal generated from the pre-pit signal area includes
at least any one of the following information for image forming, i.e.,
the outer diameter (120 mm, 80 mm) of the optical disc; recording format
of the image-recording layer (write-once, rewritable); intended purpose
(multipurpose, specific purpose); configuration of the surface of the
substrate at the side having the image-recording layer (presence or
absence of a guide groove, having a smooth surface or a rough surface);
information about the manufacturer of the disc; verification information,
etc.

[0034]In the optical disc of the invention, the image forming area may be
positioned at a deeper level the logo area. Namely, the image forming
area may be placed inside of the optical disc. In this case, the image
forming area is not exposed to the atmosphere, dust, etc, and therefore,
storability of the image forming area is excellent.

[0035]In order to further improve storability, it is preferable to provide
an image-recording layer as the image forming area, between the two
facing substrates. When an image-recording layer is provided between the
substrates, laser beam spots can be narrowed, whereby visibility can be
increased and the time period for drawing can be decreased, as compared
to recording an image on the surface. Therefore, storability of the image
forming area can be improved and the problem of working distance for slim
drives can be avoided. Furthermore, a more expensive look can be provided
to the optical disc as compared to recording on the surface.

[0036]The thickness of each of the facing substrates is preferably 0.3 mm
to 0.9 mm. By adjusting the thickness in this range, a space
corresponding to the thickness of the substrate is formed between the
laser pickup and the image-recording layer, whereby a substantial large
working distance can be secured. Therefore, even when a slim-type drive
having a small overall thickness is used, it is not necessary to separate
the position of an objective lens from the outermost surface of the
optical disc by a long distance, which gives a remarkable design
advantage for minimizing total thickness of the drive. Furthermore,
approximately the same working distance can be readily secured in both
cases when an image is recorded on the information-recording layer on the
rear side and when an image is recorded on the image-recording layer on
the obverse side.

[0037]The constitution of the optical disc of the invention may be any of
read-only type, write-once type, rewritable type, etc. Among these,
write-once type is preferable. The recording format is not specifically
limited and examples thereof may include concave and convex pit type,
phase transition type, optical magnetic type, dye type, etc. Among these,
dye type is preferable.

[0038]Furthermore, examples of the constitution of the optical disc of the
invention include the followings.

[0039](1) The first layer constitution, which comprises a first substrate,
and an information-recording layer and a reflection layer formed on the
first substrate in this order; and a second substrate, and an
image-recording layer and a reflection layer formed on the second
substrate in this order, wherein the reflection layers are adhered via an
adhesive layer.

[0040](2) The second layer constitution, which comprises a first
substrate, and an information-recording layer, a reflection layer and a
protective layer formed on the first substrate in this order; and a
second substrate, and an image-recording layer and a reflection layer
formed on the second substrate in this order, wherein the protective
layer formed on the first substrate and the reflection layer formed on
the second substrate are adhered via an adhesive layer.

[0041](3) The third layer constitution, which comprises a first substrate,
and an information-recording layer, a reflection layer and a protective
layer formed on the first substrate in this order, and a second
substrate, and an image-recording layer, a reflection layer and a
protective layer formed on the second substrate in this order, wherein
the protective layers are adhered via an adhesive layer.

[0042](4) The fourth layer constitution, which comprises a first
substrate, and an information-recording layer and a reflection layer
formed on the first substrate in this order, and a second substrate, and
an image-recording layer, a reflection layer and a protective layer
formed on the second substrate in this order, wherein the reflection
layer formed on the first substrate and the protective layer formed on
the second substrate are adhered via an adhesive layer.

[0043]In the layer constitution examples (1) to (4), a pre-pit signal area
is provided on the second substrate at the side having the
image-recording layer, and a logo area is provided on the second
substrate at the side opposite to the side having the image-recording
layer.

[0044]The above-mentioned examples of the layer constitutions (1) to (4)
are provided merely for the purpose of explanation, and an optical
enhance layer, a protective layer, etc. can be provided where necessary.
Each of the layers may be constituted by a single layer or plural layers.
The optical disc of the invention may be one having an outer diameter of
120 mm or one having an outer diameter of 80 mm. Furthermore, the optical
disc may be of card type or may have various modified shapes. The logo
area may be provided on two positions, i.e., inside circumference and
outside circumference, and may have any shape other than ring type. In
case where the optical disc has an outer diameter of 80 mm, the outer
logo area is not always necessary.

[0045]FIG. 1A is a partial cross-sectional view that shows an example of
the layer constitution of optical disc 500 of the invention. The optical
disc 500 includes a first laminate 520 including a first substrate 512,
and an information-recording layer 514 and a first reflection layer 516
formed on the first substrate 512 in this order; and a second laminate
528 including a second substrate 522, and an image-recording layer 524 on
which a visible image is recorded by irradiation of laser light and
second reflection layer 526 formed on the second substrate in this order.
The first laminate 520 and the second laminate 528 are adhered via an
adhesive layer 530 so that the first reflection layer 516 and the second
reflection layer 526 faces each other.

[0046]A pre-pit signal area 600 on which pre-pits have been formed is
provided on the face of the second substrate on which the image-recording
layer is formed. Furthermore, logo areas 610A and 610B are provided in a
concentric fashion on the face opposite to the face on which the
image-recording layer is formed of the second substrate 522 by a printing
method such as screen printing, offset printing, etc.

[0047]As shown in FIG. 1A, the logo area may be provided on the surface of
the optical disc 500 by printing, etc. Alternatively, as shown in FIG.
1B, a logo area 620 that indicates visible information may be formed by
providing a indented portion (a concavity and convexity pattern) on the
second substrate and forming a reflection layer thereon. According to
such embodiment, so-called a pit art can be formed, whereby design
property can be improved. In this case, the reflection layer can be
formed by extending the reflection layer lined on the image-recording
layer, whereby steps for forming the layers can be decreased. The
reference characters in FIG. 1B that are same as those of FIG. 1A have
the same functions. Therefore, explanations of such reference characters
are abbreviated.

[0048]As shown in the examples of FIGS. 1A and 1B, so long as the optical
disc of the invention has a logo area, a pre-pit signal area and an image
forming area, the relationship of the positions of these areas is not
specifically limited. In view of the storability of the image forming
area, it is preferable that the image forming area is positioned at a
deeper level than the logo area (i.e., the image forming area is
positioned at a layer that is further from the outer surface than the
logo area, for example, the image forming area is positioned at an inner
layer than a layer having the logo area). Furthermore, it is preferable
that the pre-pit signal area is positioned at a deeper level than the
logo area. In view of the visibility of the logo area and the formed
image, it is preferable that the optical disc includes the logo area, the
pre-pit signal area and the image forming area provided in this order
from the inside circumference of the optical disc.

[0049]When the logo area, the pre-pit signal area and the image forming
area are provided in this order from the inside circumference of the
optical disc, and the pre-pit signal area is positioned at a deeper level
than the logo area, it is preferable that the outer circumference of the
logo area is positioned closer to the outer circumference of the optical
disc than the inner circumference of the pre-pit signal area as shown,
for example, in FIGS. 1A, 3A, 3B and 3C. By this arrangement, it is
possible to attain excellent appearance and also it is possible to ease
required positioning accuracy thereby improving suitability for
inexpensive mass production and yield.

[0050]The optical disc may include, at an outer circumferential area, a
printing area (which may be a logo area). In this case, the optical disc
may include a logo area, a pre-pit signal area, an image forming area and
another logo area, in this order from the inside circumference of the
optical disc, as shown in FIG. 1A.

[0051]Specifically, the constitutions as shown in FIGS. 2A, 2B and 2C, and
3A, 3B and 3C are preferable. Namely, as shown in FIGS. 2A, 2B and 2C, it
is preferable to form a logo area 702 on the label side of a substrate
720, and to form a pre-pit signal area 704 and an image recording area
(image-recording layer) 706 toward the outer circumference from the
pre-pit signal area 704. Furthermore, the partial sectional structure as
shown in FIGS. 3A, 3B and 3C are preferable. That is, it is preferable to
form the image recording area 706 and the pre-pit signal area 704, in
this order from the outer circumference, between the substrate 710 and
the substrate 720. Moreover, it is preferable that the logo area 702 is
provided on the upper surface of the substrate 720. According to such
constitution, the innermost edge portion of the optical disc can be
shielded and the visual effect to users can be improved.

[0052]In FIGS. 3A, 3B and 3C, the radius r0, which is an inner
circumference end of the logo area 702, is preferably 8 mm to 21 mm, and
the radius r1, which is an outer circumference end, is preferably 21 mm
to 23 mm (wherein r0<r1). The radius r2, which is an inside
circumference end of the pre-pit signal area 704, is preferably 19 mm to
22 mm, and the radius r3, which is an outside circumference end, is
preferably 22 mm to 25 mm (wherein r2<r3). The radius r1 may be
smaller than the radius r2 (r1<r2), the same as radius r2 (r1=r2) or
larger than radius r2 (r1>r2). The radius r1 is preferably the same as
radius r2 or larger (r1≧r2), and more preferably, as shown in
FIGS. 3A, 3B and 3C, the radius r1 is larger than the radius r2
(r1>r2). The radius r4, which is an inside circumference end of the
image recording area 706, is preferably in the range of 23 mm to 25 mm
(wherein r3≦r4), and the radius r5, which is an outer
circumference end, corresponds to the outermost circumference of the
image recording area 706 (wherein r4<r5).

[0053]As shown in FIGS. 3B and 3C, the logo area may be constituted by two
or more layers. Namely, as shown in FIG. 3B, a logo area 702a may be
formed using the logo area 702 as a ground. Alternatively, as shown in
FIG. 3C, a logo area 702b, the logo area 702 that acts as a ground layer
and the logo area 702a may be formed in this order. According to the
embodiment as shown in FIG. 3B, a logo formed on the logo area 702a can
be prevented from being seen from the side of the substrate 710.
According to the embodiment as shown in FIG. 3C, the logo formed on the
logo area 702a can be seen visually from the side of the substrate 720,
and a logo formed on the logo area 702b can be seen visually from the
side of the substrate 710.

[0054]Hereinafter each of the layers and the procedures for forming the
layers are explained with referring to the layer constitutions of FIGS.
1A and 1B.

Information-Recording Layer

[0055]The information-recording layer is a layer on which code information
(coded information) such as digital information is recorded. The type of
the information-recording layer is not particularly limited, and may be
the concave and convex pit type, the dye type, the phase change type, the
magnetooptical type, or the like.

[0056]The dye contained in the dye-type information-recording layer may
be, for example, a cyanine dye, an oxonol dye, a metal complex dye, an
azo dye, or a phthalocyanine dye. Among these dyes, an azo dye and an
oxonol dye are preferable.

[0057]The dyes disclosed in the following documents are also usable in the
invention: JP-A Nos. 4-74690, 8-127174, 11-53758, 11-334204, 11-334205,
11-334206, 11-334207, 2000-43423, 2000-108513, and 2000-158818.

[0058]The recording substance is not limited to dyes, and the recording
substance may be an organic compound such as a triazole compound, a
triazine compound, a cyanine compound, a merocyanine compounds, an
aminobutadiene compound, a phthalocyanine compound, a cinnamic acid
compound, a viologen compound, an azo compound, an oxonolbenzoxazole
compound, or a benztriazole compound. Among these compounds, a cyanine
compound, an aminobutadiene compound, a benztriazole compound, and a
phthalocyanine compound are preferable.

[0059]The information-recording layer is formed by the following
processes: a recording substance such as a dye, a binder, and the like
are dissolved in a solvent to form a coating liquid, and the coating
liquid is applied to the surface of the substrate to form a film, and the
film is dried to form an information-recording layer. The concentration
of the recording substance in the coating liquid is generally 0.01 to 15%
by mass, preferably 0.1 to 10% by mass, more preferably 0.5 to 5% by
mass, and still more preferably 0.5 to 3% by mass.

[0060]The information-recording layer may be formed by a method such as
deposition, sputtering, CVD, or coating using a solvent. Coating using a
solvent is a preferable method.

[0061]The solvent of the coating liquid may be selected from: esters such
as butyl acetate, ethyl lactate, and cellosolve acetate; ketones such as
methyl ethyl ketone, cyclohexanone, and methyl isobutyl ketone;
chlorinated hydrocarbons such as dichloromethane, 1,2-dichloroethane, and
chloroform; amides such as dimethylformamide; hydrocarbons such as
methylcyclohexane; ethers such as dibutyl ether, diethyl ether,
tetrahydrofuran, and dioxane; alcohols such as ethanol, n-propanol,
isopropanol, n-butanol, and diacetone alcohol; fluorine-based solvents
such as 2,2,3,3-tetrafluoropropanol; and glycol ethers such as ethylene
glycol monomethyl ether, ethylene glycol monoethyl ether, and propylene
glycol monomethyl ether.

[0062]The solvent may be selected in consideration of the solubility of
the dye to be used in the solvent, and only a single solvent may be used
or two or more solvents may be used in combination. The coating liquid
may further include various additives such as antioxidants, UV absorbers,
plasticizers, and lubricants, in accordance with the purpose.

[0064]When a binder is used as a component of the information-recording
layer material, the mass ratio of the amount of the binder to the amount
of the dye is preferably in the range of 0.01 to 50, and more preferably
in the range of 0.1 to 5.

[0065]The coating liquid may be coated by a spray coating method, a spin
coating method, a dip coating method, a roll coating method, a blade
coating method, a doctor roll method, or a screen printing method. The
recording layer may be comprised of a single layer or two or more layers.
The thickness of the information-recording layer is generally in the
range of 10 to 500 nm, preferably in the range of 15 to 300 nm, and more
preferably in the range of 20 to 150 nm.

[0066]An antifading agent may be included in the information-recording
layer so as to improve the light resistance of the information-recording
layer, and the antifading agent may be selected from various antifading
agents. The antifading agent is generally a singlet-oxygen quencher. The
singlet-oxygen quencher may be selected from singlet-oxygen quenchers
disclosed in known published documents such as patent specifications.
Specific examples thereof include the singlet-oxygen quenchers disclosed
in JP-A No. 58-175693, 59-31194, 60-18387, 60-19586, 60-19587, 60-35054,
60-36190, 60-36191, 60-44554, 60-44555, 60-44389, 60-44390, 60-54892,
60-47069, 68-209995, and 4-25492, and Japanese Patent Publication (JP-B)
Nos. 1-38680 and 6-26028, German Patent No. 350399, and Nihon
Kagakukaishi (1992 October) p. 1141.

[0067]The amount of the antifading agent to be used such as a
singlet-oxygen quencher is generally 0.1 to 50% by mass based on the
amount of the dye, preferably 0.5 to 45% by mass, more preferably 3 to
40% by mass, and still more preferably 5 to 25% by mass based on the
amount of the dye.

[0069]The thickness of the phase change information-recording layer is
preferably 10 to 50 nm, and more preferably 15 to 30 nm.

[0070]The phase change information-recording layer can be formed by a
sputtering method or a vapor-phase thin film deposition method such as a
vacuum-deposition method.

First Substrate and Second Substrate

[0071]In the optical disc of the invention, the first substrate and the
second substrate each may be selected from various materials known as the
substrates of the conventional optical discs. Pre-pit(s) may be formed on
the image-recording layer side of the second substrate.

[0072]The substrate material may be, for example, glass, polycarbonate, an
acrylic resin such as polymethyl methacrylate, a vinyl-chloride-based
resin such as polyvinyl chloride or a vinyl chloride copolymer, an epoxy
resin, amorphous polyolefin, or polyester. Two or more of the above
materials may be used together, if desired. The material may be used as a
film-like substrate or a rigid substrate. Among the above materials,
polycarbonate is preferable from the viewpoints of the moisture
resistance, the dimensional stability, the price, and the like.

[0073]The second substrate may be prepared via a step for forming a
substrate comprising a pre-pit on the surface on which an image-recording
layer is formed, using a stamper of the invention as mentioned above. The
height of the convexity, which corresponds to the depth of the pre-pit,
can be controlled by adjusting the film thickness of the photoresist.

[0074]As mentioned above, the thickness of the first substrate and the
second substrate is preferably 0.3 mm to 0.9 mm, more preferably 0.5 mm
to 0.7 mm, and still more preferably 0.55 mm to 0.65 mm. It is preferable
that the first substrate has a groove or a servo signal for tracking. The
second substrate may be a substrate having such groove or servo signal
for tracking. The track pitch of the groove on the first substrate is
preferably in the range of 300 nm to 1600 nm, more preferably in the
range of 310 nm to 800 nm. The depth of the groove is preferably in the
range of 15 nm to 200 nm, and more preferably in the range of 25 nm to
180 nm.

[0075]For recording a high definition image or a computer hologram image
on the image-recording layer, the image recording area of the second
substrate may also have a groove for tracking. In this case, the track
pitch of the groove is preferably in the range of 0.3 μm to 100 μm,
more preferably in the range of 0.6 μm to 50 μm, and still more
preferably in the range of 0.7 μm to 20 μm, in view of intensity
distribution of recording laser.

[0076]When tracking is carried out during image recording and the
thickness of the substrate on which laser light falls is 0.6 mm, the
depth of the groove is preferably 50 nm to 250 nm, more preferably 80 nm
to 200 nm, and still more preferably 100 nm to 180 nm. The width of the
groove is preferably 100 nm to 600 nm, more preferably 150 nm to 500 nm,
and further preferably 200 nm to 450 nm. The optimum range of the shape
of the groove may vary depending on the wavelength of laser light, NA,
thickness of the substrate, etc.

[0077]An undercoat layer may be provided on the surface of the first
substrate (the surface having the groove (in the case of ROM, the surface
having a pit)), for the purposes of improving the planarity and adhesion
and preventing the degradation of the information-recording layer.

[0078]Examples of the material of the undercoat layer include:
high-molecular weight substances such as polymethyl methacrylate, acrylic
acid-methacrylic acid copolymers, styrene-maleic anhydride copolymers,
polyvinyl alcohol, N-methylol acrylamide, styrene-vinyltoluene
copolymers, chlorosulfonated polyethylene, nitrocellulose, polyvinyl
chloride, chlorinated polyolefin, polyester, polyimide, vinyl
acetate-vinyl chloride copolymers, ethylene-vinyl acetate copolymers,
polyethylene, polypropylene, and polycarbonate; and surface modifiers
such as silane coupling agents. The undercoat layer may be formed by:
dissolving or dispersing the material for the undercoat layer in an
appropriate solvent to form a coating liquid, and then coating the
substrate surface with the coating liquid by a coating method such as
spin coating, dip coating, or extrusion coating.

[0079]The thickness of the undercoat layer is generally 0.005 to 20 μm,
more preferably 0.01 to 10 μm.

[0080]Meanwhile, in order to avoid reflection of surroundings by mirror
surface reflecting light on the visible image formed on the
image-recording layer, it is preferable to provide surface roughening
treatment on the surface of the second substrate on which an
image-recording layer is formed.

[0081]Although the method for the surface roughening treatment on the
second substrate may be any of various methods and is not specifically
limited, it is preferable to apply any of the first to the fifth surface
roughening treatments as mentioned below.

[0082](1) The first surface roughening treatment includes surface
roughening of the surface of the second substrate on which an
image-recording layer is formed, using a stamper in which surface
roughening treatment have been provided on one surface to which the
second substrate contacts. Specifically, a stamper, which is used for the
preparation of the second substrate, is firstly subjected to surface
roughening treatment. The method for surface roughening treatment
comprises, for example, blast treatment such as sand blast, by which a
desired roughness can be afforded. Alternatively, chemical treatment as
the fifth surface roughening treatment mentioned below may be used. The
stamper is then placed on a mold so that the roughened surface contacts
to a resin material for the second substrate, and the material is formed
by a known method, whereby the second substrate having a roughened
surface on only one side can be prepared. It is preferable that the
"desired roughness" has, for example, the maximum height (Rz) of the
surface of 0.3 μm to 5 μm, and the average length (RSm) of the
roughness curve element of 10 μm to 500 μm.

[0083](2) The second surface roughening treatment includes surface
roughening of the surface of the second substrate on which an
image-recording layer is formed, using a mold in which surface roughening
treatment has been provided on one surface to which the second substrate
contacts, after forming of the second substrate. Specifically, surface
roughening treatment is provided on one surface (main surface) of a mold
for forming the second substrate. The method for surface roughening
treatment is similar to that for the first surface roughening treatment.
By forming according to a known method using the mold, the second
substrate having a roughened surface on only one side can be prepared.

[0084](3) The third surface roughening treatment includes forming the
second substrate, applying a resin in which particles have been dispersed
on the surface of the second substrate on which an image-recording layer
is formed, curing the resin, whereby roughening the surface of the second
substrate on which an image-recording layer is formed. Examples of the
resin include acrylate UV-curable resin, epoxy thermosetting resin,
isocyanate thermosetting resin, etc.

[0085]Examples of the particles include inorganic particles such as
SiO2, Al2O3, etc., polycarbonate resin particles, acrylic
resin particles, etc. The volume average particle size of the particles
is preferably 0.3 μm to 200 μm, and more preferably 0.6 μm to
100 μm. By adjusting the particle size and the amount to be added of
the particles, desired roughness can be provided on the roughened
surface.

[0086](4) The fourth surface roughening treatment comprises forming the
second substrate, providing mechanical processing treatment on the
surface of the second substrate on which an image-recording layer is
formed, whereby roughening the surface of the second substrate on which
an image-recording layer is formed. Although examples of the mechanical
processing treatment may include various treatments, it is preferable to
apply blast treatment such as sand blast.

[0087](5) The fifth surface roughening treatment include, forming the
second substrate, providing chemical treatment on the surface of the
second substrate on which an image-recording layer is formed, whereby the
surface of the second substrate on which an image-recording layer is
formed is roughened. Examples of the chemical treatment include etching
treatment by applying a solvent on one surface of the second substrate
after forming, or by spraying a solvent using a spray, etc. Preferable
examples of the solvent include organic solvents such as
dimethylformamide, etc., as well as acidic solvents such as nitric acid,
hydrochloric acid, sulfuric acid, etc. Desired roughness can be obtained
by adjusting the normality of the acidic solvent or time for applying.

First Reflection Layer and Second Reflection Layer

[0088]A first reflection layer is preferably provided adjacent to the
information-recording layer and a second reflection layer is preferably
provided adjacent to the image-recording layer, for the purpose of
improving the reflectance at the time of reproduction of information. The
light-reflecting substance, which is the material of the reflection
layer, is a substance having a high laser light reflectance. Examples
thereof include metals and semimetals such as Mg, Se, Y, Ti, Zr, Hf, V,
Nb, Ta, Cr, Mo, W, Mn, Re, Fe, Co, Ni, Ru, Rh, Pd, Ir, Pt, Cu, Ag, Au,
Zn, Cd, Al, Ga, In, Si, Ge, Te, Pb, Po, Sn, and Bi, and stainless steel.
Only a single light-reflecting substance may be used, or a combination of
two or more light-reflecting substances may be used, or an alloy of two
or more light-reflecting substances may be used. The light-reflecting
substance is preferably Cr, Ni, Pt, Cu, Ag, Au, Al, or stainless steel,
more preferably metallic Au, metallic Ag, metallic Al or an alloy
thereof, still more preferably metallic Ag, metallic Al, or an alloy
thereof. The reflection layer may be formed on the substrate or on the
recording layer, for example by depositing, sputtering, or ion-plating a
light-reflecting substance. The thickness of the light reflection layer
is generally 10 to 300 nm, preferably 50 to 200 nm. When the disc formed
on the first substrate and the disc formed on the second substrate are
adhered to each other such that the first and second reflection layers
face each other and a UV-curable adhesive is used, the thickness of the
first reflection layer or the second reflection layer is preferably 100
nm or less, and more preferably 70 nm or less.

Adhesive Layer

[0089]The adhesive layer is a layer for adhering the first laminate 520
and the second laminate 528 in FIGS. 1A and 1B, which is positioned
between the first reflection layer 516 and the second reflection layer
526. Examples of the adhesive used for the adhesive layer may include
known UV-curable resin, etc.

Image-Recording Layer

[0090]On the image-recording layer, a visible image (visible information)
desired by the user is recorded such as a character, a figure, or a
picture. The visible image may be the disc title, content information,
thumbnail of the content, a related picture, a design picture,
information on the copyright, the recording date, the recording method,
the recording format, or a bar code.

[0091]The visible image to be recorded on the image-recording layer refers
to a visually recognizable image, and may be any visually recognizable
information such as a character, a character string, a picture, and a
figure. The visible image may be a textual information such as user
authorization information, permitted use period designation information,
information on the designated number of permitted use, rental
information, resolution designation information, layer designation
information, user designation information, information on the owner of
the copyright, the copyright number information, manufacturer
information, manufacturing date information, selling date information,
shop or seller information, use set number information, region
designation information, language designation information, use
designation information, product user information, or user number
information.

[0092]The image recording layer may be any layer as long as it can record
visible image information such as letters, images, drawings, etc. by
irradiation of laser light. In view of formation of clear pits, it is
preferable that the image-recording layer includes a dye compound.
Examples of the materials of the dye compound that can be suitably used
include the dyes as explained for the above-mentioned
information-recording layer. In this case, in view of costs, etc., it is
preferable that the image-recording layer is formed by spin coating
method using a coating liquid including a dye compound.

[0093]In the optical disc of the invention, the information-recording
layer component (a dye or a phase change recording material) may be the
same as or different from the component of the image-recording layer. The
components in the respective layers are preferably different since the
characteristics desired for the information-recording layer is different
from the characteristics desired for the image-recording layer.
Specifically, the component of the information-recording layer is
preferably excellent in the recording and reproducing characteristics,
and the component of the image-recording layer is preferably such a
substance that the recorded image has a high contrast. When a dye is used
in the image-recording layer, the dye is preferably, among the dyes
described above, a cyanine dye, a phthalocyanine dye, an azo dye, an
azo-metal complex, or an oxonol dye, from the viewpoint of improving the
contrast of the recorded image.

[0095]The image recording layer may be formed by dissolving the dye in a
solvent to form a coating liquid and then applying the coating liquid.
The solvent may be selected from the solvents cited above as examples of
the solvent used in the preparation of the coating liquid for the
information-recording layer. Other additives and the coating method are
similar to the above-described additives and coating method used for the
formation of the information-recording layer.

[0096]The thickness of the image-recording layer is preferably 0.01 to 2
μm, more preferably 0.05 to 1 μm, and still more preferably 0.1 to
0.5 μm.

[0097]Hereinafter, the protective layer will be described.

Protective Layer

[0098]A protective layer may be provided in order to protect the first
reflection layer or the information-recording layer physically and
chemically.

[0099]Examples of the material used in the protective layer include
inorganic substances such as ZnS, ZnS--SiO2, SiO, SiO2,
MgF2, SnO2, and Si3N4; and organic substances such as
thermoplastic resins, thermosetting resins, and UV-setting resins.

[0100]When the protective layer material is a thermoplastic resin or a
thermosetting resin, the protective layer may be formed by: dissolving
the thermoplastic or thermosetting resin in an appropriate solvent to
form a coating liquid, and then coating the coating liquid followed by
drying. When the protective layer material is a UV-setting resin, the
protective layer may be formed by: dissolving the UV-setting resin in an
appropriate solvent to form a coating liquid, and then coating the
coating liquid, and then irradiating the coating film with UV light to
cure the film. In the above methods, the coating liquids may further
include various additives such as antistatic agents, antioxidants, and UV
absorbers, in accordance with the purpose. The thickness of the
protective layer is preferably 0.1 μm to 1 mm.

[0101]As mentioned above, the optical disc of the invention can be applied
to so-called a read-only optical disc, which includes the first substrate
having a recording portion (pits) on which reproducible information has
been recorded by laser light.

Image Forming Method

[0102]The image forming method of the invention is a method of forming a
visible image on an optical disc by irradiation of laser light,
comprising detecting a pre-pit signal from a pre-pit signal area formed
on the optical disc of the invention, and forming the visible image based
on the result of the detection. First, an optical disc recording
apparatus that can be applied to the image forming method of the
invention is explained below.

Optical Disc Recording Apparatus

[0103]Image recording on the image-recording layer and optical information
recording on the information-recording layer may be conducted by a single
optical disc drive (a recording apparatus) having functions of recording
on the respective recording layers. When a single optical disc drive is
used, recording on one of the image-recording layer and the
information-recording layer is conducted, and then the disc is turned
over, so that the recording on the other recording layer can be
conducted.

[0104]An optical disc recording apparatus for which the optical disc of
the invention can be used suitably is, for example,

(1) An optical disc recording apparatus that records information by
irradiating the recordable side (for example, the dye recording layer
(recording layer)) of an optical disc with a laser light, the recording
apparatus comprising: an optical pickup that irradiates the laser light
onto the optical disc; an irradiation position adjusting unit that
adjusts the position of irradiation of the laser light by the optical
pickup onto the optical disc; an image formation control unit that
controls the optical pickup and the irradiation position adjusting unit
such that a visible image corresponding to image information is formed on
the image-recording layer of the optical disc when the optical disc
having the recordable side on one side and an image-recording layer on
the other side is set with the image-recording layer facing the optical
pickup; and a beam spot control unit that controls the optical pickup
such that the beam spot size of the laser light irradiated onto the
image-recording layer by the optical pickup at the formation of the
visible image is greater than the beam spot size of the laser light
irradiated by the optical pickup onto the recordable side at the
recording of information.

[0105]According to this arrangement, when the image-recording layer of the
optical disc is irradiated with the laser light in accordance with image
information, a visible image corresponding to the image information can
be formed by change in the reflectance of the image-recording layer
caused by the change in the absorbance of the image-recording layer.
Since the laser light is irradiated onto the image-recording layer of the
optical disc with an increased beam spot size upon formation of the
visible image, a larger area is irradiated with the laser light during
one revolution of the optical disc, and the time required to form the
visible image can be reduced. An excellent image can be obtained when
this method is employed on the optical disc of the invention.
Furthermore, the above image management information can be obtained by
pre-pit signals from the pre-pit signal area of the optical disc. In the
optical disc recording apparatuses of other embodiments described below,
the administrative information of the image can be obtained in the same
way.

[0106]The optical disc recording apparatus of another aspect is

(2) an optical disc recording apparatus that records information by
irradiating the recordable side of an optical disc with a laser light,
the recording apparatus comprising: an optical pickup that irradiates the
laser light onto the optical disc; an irradiation position adjusting unit
that adjusts the position of irradiation of the laser light by the
optical pickup onto the optical disc; an image formation control unit
that controls the optical pickup and the irradiation position adjusting
unit such that a visible image corresponding to image information is
formed on the image-recording layer of the optical disc when the optical
disc having the recordable side on one side and an image-recording layer
on the other side is set with the image-recording layer facing the
optical pickup, and such that the intensity of the laser light irradiated
onto the image-recording layer is selected, based on the image
information, from a first intensity which hardly changes the
image-recording layer and a second intensity which is greater than the
first intensity and which changes the image-recording layer; and a servo
unit that detects information about the laser light irradiated by the
optical pickup onto the optical disc and controls the optical pickup
based on the detection results such that the desired laser light is
irradiated. When the intensity of the laser light irradiated by the
optical pickup under the control based on the image information is
maintained at the second intensity over a predetermined period of time,
the image formation control unit changes the intensity of the laser light
irradiated from the optical pickup to the first intensity irrespective of
the image information and maintains the first intensity for a
predetermined period of time. The servo unit controls the optical pickup
based on the detection results of the information about the laser light
irradiated at the first intensity.

[0107]According to this arrangement, when the laser light is irradiated
onto the image-recording layer of the optical disc based on image
information, the reflectance changes as the absorbance of the
image-recording layer changes, whereby a visible image corresponding to
the image data can be formed. At visible image formation, even when the
intensity of the laser light corresponding to the image data is
maintained for a long time at the second intensity that changes the
image-recording layer, the laser light at the first intensity that hardly
changes the image-recording layer is irradiated for laser light control
irrespective of the image data, so that laser light control based on the
irradiation results can be conducted. An excellent image can be obtained
when this method is employed on the optical disc of the invention.

[0108]The optical disc recording apparatus of another aspect is

(3) an optical disc recording apparatus that records information by
irradiating the recordable side of an optical disc with a laser light,
the recording apparatus comprising: an optical pickup that irradiates the
laser light onto the optical disc; an irradiation position adjusting unit
that adjusts the position of irradiation of the laser light by the
optical pickup onto the optical disc; an image formation control unit
that controls the optical pickup and the irradiation position adjusting
unit such that a visible image corresponding to image information is
formed on the recordable side of the optical disc, and such that the
intensity of the laser light irradiated onto the recordable side is
selected, based on the image information, from a first intensity which
hardly changes the recordable side and a second intensity which is
greater than the first intensity and which changes the recordable side;
and a servo unit that detects information about the laser light
irradiated by the optical pickup onto the optical disc and controls the
optical pickup based on the detection results such that the desired laser
light is irradiated. When the intensity of the laser light irradiated by
the optical pickup under the control based on the image information is
maintained at the second intensity over a predetermined period of time,
the image formation control unit changes the intensity of the laser light
irradiated from the optical pickup to the first intensity irrespective of
the image information and maintains the first intensity for a
predetermined period of time. The servo unit controls the optical pickup
based on the detection results of the information about the laser light
irradiated at the first intensity.

[0109]According to this arrangement, when the laser light is irradiated
onto the image-recording layer of the optical disc based on image
information, a visible image corresponding to the image data can be
formed by the change in the reflectance the recording layer. At visible
image formation, even when the intensity of the laser light corresponding
to the image data is maintained for a long time at the second intensity
that changes the recordable side, the laser light at the first intensity
that hardly changes the recordable side is irradiated for laser light
control irrespective of the image data, so that laser light control based
on the irradiation results can be conducted. An excellent image can be
obtained when this method is employed on the optical disc of the
invention.

[0110]The optical disc recording apparatus of another aspect is

(4) an optical disc recording apparatus that records information by
irradiating the recordable side of an optical disc with a laser light,
the recording apparatus comprising: an optical pickup that irradiates the
laser light onto the optical disc; an irradiation position adjusting unit
that adjusts the position of irradiation of the laser light by the
optical pickup onto the optical disc; an image formation control unit
that controls the optical pickup and the irradiation position adjusting
unit such that a visible image corresponding to image information is
formed on the image-recording layer of the optical disc when the optical
disc having the recordable side on one side and an image-recording layer
on the other side is set with the image-recording layer facing the
optical pickup; and a relative position adjustment unit that adjusts the
relative positional relationship between the optical pickup and the side
of the optical disc facing the optical pickup based on whether the side
of the optical disc facing the optical pickup is the image-recording
layer or the recordable side when the optical disc is set in the optical
disc recording apparatus.

[0111]According to this arrangement, when the laser light is irradiated
onto the image-recording layer of the optical disc based on image
information, a visible image corresponding to the image information can
be formed by change in reflectance accompanying the change in the
absorbance of the image-recording layer. When the optical disc is loaded,
the positional relationship between the optical pickup and the side
facing the optical pickup can be adjusted based on whether the optical
pickup faces the image-recording layer or the recordable side. Therefore,
even if the distance between the optical pickup and the side facing the
optical pickup varies depending on whether the optical disc is set with
its recordable side facing the optical pickup or with its image-recording
layer facing the optical pickup, problems derived from the variation of
the distance, which may impair various types of controls such as focus
control, can be avoided. An excellent image can be obtained when this
method is employed on the optical disc of the invention.

[0112]The optical disc recording apparatus of another aspect is

(5) an optical disc recording apparatus that records information by
irradiating the recordable side of an optical disc with a laser light,
the recording apparatus comprising: an optical pickup that irradiates the
laser light onto the optical disc; an irradiation position adjusting unit
that adjusts the position of irradiation of the laser light by the
optical pickup onto the optical disc; a servo unit that controls the
irradiation position adjusting unit when the optical disc having a
recordable side with a spiral guide groove on one side and an
image-recording layer on the other side is set with the image-recording
layer facing the optical pickup, such that the laser light is irradiated
along the guide groove based on the reflection, on the optical disc, of
the laser light irradiated by the optical pickup; and image formation
control unit that controls the laser light irradiated from the optical
pickup while the irradiation position of the laser light is moved along
the guide groove by the servo unit, such that a visible image
corresponding to image information is formed on the image-recording layer
of the optical disc. An excellent image can be obtained when this method
is employed on the optical disc of the invention.

[0113]According to this arrangement, when the laser light is irradiated
onto the image-recording layer of the optical disc based on the image
information, the reflectance is changed as the absorbance of the
image-recording layer is changed, and a visible image corresponding to
the image information can be formed. In this process, the visible image
can be formed without conducting a more complex laser-light irradiation
position adjustment than when recording is conducted on the recordable
side, such as detecting the guide groove provided on the recordable side
and moving the laser-light irradiation position along the detected guide
groove.

[0114]The optical disc recording apparatus of another aspect is

(6) an optical disc recording apparatus that records information by
irradiating the recordable side of an optical disc with a laser light,
the recording apparatus comprising: an optical pickup that irradiates the
laser light onto the optical disc; a rotation driving unit that rotates
the optical disc; a clock signal output unit that outputs clock signals
having a frequency corresponding to the speed of the rotation of the
optical disc driven by the rotation driving unit; an image formation
control unit that controls the optical pickup such that a visible image
corresponding to image information is formed on the image-recording layer
of the optical disc when the optical disc having the recordable side on
one side and an image-recording layer on the other side is set with the
image-recording layer facing the optical pickup, the image formation
control unit also controlling the laser light irradiated from the optical
pickup based on the image information at each cycle of the clock signal
from the signal output unit; a rotation detecting unit that detects that
the optical disc has been rotated by the rotation driving unit for one
revolution from the predetermined reference position; and an irradiation
position adjusting unit that moves the irradiation position of the laser
light emitted from the optical pickup for a predetermined distance in the
predetermined radius direction on the optical disc set in the optical
disc recording apparatus when each revolution of the optical disc from
the predetermined reference position is detected by the rotation
detecting unit upon irradiation of laser light by the optical pickup for
the formation of the visible image on the image-recording layer of the
optical disc.

[0115]According to this arrangement, when the laser light is irradiated
onto the image-recording layer of the optical disc based on the image
information, the reflectance is changed as the absorbance of the
image-recording layer is changed, and a visible image corresponding to
the image information can be formed. In the visible image forming
process, the laser light irradiation control is conducted for visible
image formation at every cycle of the clock signal having a frequency
corresponding to the rotation speed of the optical disc, i.e., at every
time the optical disc rotates for a certain angle; therefore, a visible
image whose contents (e.g., density) are in accordance with the image
data can be formed at each positions of even angular spacing. An
excellent image can be obtained when this method is employed on the
optical disc of the invention.

[0116]The optical disc recording apparatus of another aspect is

(7) an optical disc recording apparatus that records information by
irradiating the recordable side of an optical disc with a laser light,
the recording apparatus comprising: an optical pickup that irradiates the
laser light onto the optical disc; a rotation driving unit that rotates
the optical disc; a rotation detecting unit that detects that the optical
disc has been rotated by the rotation driving unit for one revolution
from the predetermined reference position; an image formation control
unit that controls the optical pickup such that a visible image
corresponding to image information is formed on the image-recording layer
of the optical disc when the optical disc having the recordable side on
one side and an image-recording layer on the other side is set with the
image-recording layer facing the optical pickup; and an irradiation
position adjusting unit that moves the irradiation position of the laser
light emitted from the optical pickup for a predetermined distance in the
predetermined radius direction on the optical disc set in the optical
disc recording apparatus when each revolution of the optical disc from
the predetermined reference position is detected by the rotation
detecting unit upon irradiation of laser light by the optical pickup for
the formation of the visible image on the image-recording layer of the
optical disc. The image formation control unit orders the optical pickup
to emit laser light such that the visible image is formed from the
predetermined reference position of the image-recording layer of the
optical disc rotated by the rotation driving unit, and such that the
laser light for visible image formation is not emitted when the
laser-light irradiation position is within the range from a predetermined
amount before the predetermined reference position of the optical disc to
the predetermined reference position.

[0117]According to this arrangement, when the laser light is irradiated
onto the image-recording layer of the optical disc based on the image
information, the reflectance is changed as the absorbance of the
image-recording layer is changed, and a visible image corresponding to
the image information can be formed. In the visible image forming
process, while the optical disc is rotated, the visible image is formed
by irradiation of the laser light from the reference position on the
optical disc; however, the laser light irradiation for visible image
formation is not conducted on the region just before the laser light
irradiation position returns to the reference position. Therefore, even
when, for certain reasons such as unstable rotation of the optical disc,
laser light irradiation control is disturbed and the laser light
irradiation is conducted for more than one revolution of the optical disc
from the reference position, so that the irradiation position passes the
reference position again (i.e., the laser light irradiation position
moves to the position overlapping the position which has been already
irradiated with the laser light), the irradiation of the laser light for
visible image formation is prevented, whereby the deterioration of the
quality of the resultant visible image can be prevented.

[0118]The optical disc recording apparatus of another aspect is

(8) An optical disc recording apparatus that records information by
irradiating the recordable side of an optical disc with a laser light,
the recording apparatus comprising: an optical pickup that irradiates the
laser light onto the optical disc; an irradiation position adjusting unit
that adjusts the position of irradiation of the laser light by the
optical pickup onto the optical disc; an disc identifying unit that
obtains disc identifying information for identifying the type of the
optical disc set in the optical disc recording apparatus; and an image
formation control unit that controls the optical pickup and the
irradiation position adjusting unit such that a visible image
corresponding to image information is formed on the image-recording layer
of the optical disc when the optical disc having the recordable side on
one side and an image-recording layer on the other side is set with the
image-recording layer facing the optical pickup, the image formation
control unit controlling the optical pickup and the irradiation position
adjusting unit according to the type of the optical disc identified by
the disc identifying unit.

[0119]According to this arrangement, when the laser light is irradiated
onto the image-recording layer of the optical disc based on the image
information, the reflectance is changed as the absorbance of the
image-recording layer is changed, and a visible image corresponding to
the image information can be formed. In this visible-image forming
process, control for visible image formation can be performed in
accordance with the type of the loaded disc.

[0120]The optical disc recording apparatus of another aspect is

(9) an optical disc recording apparatus comprising: an optical pickup that
irradiates laser light to an optical disc; a modulating unit that
modulates information supplied from the outside; and a laser light
control unit that controls the laser light irradiated from the optical
pickup based on the information supplied from the modulating unit. The
optical disc recording apparatus further comprises: an inhibiting unit
that inhibits the modulation of the image information supplied from the
outside by the modulating unit when a visible image is formed on the
image-recording layer of the optical disc having the recordable side on
one side and the image-recording layer on the other side; and an image
formation control unit that controls the laser light control unit such
that a visible image corresponding to unmodulated image information
supplied from the modulating unit is formed on the image-recording layer
of the optical disc when the optical disc is set with the image-recording
layer facing the optical pickup.

[0121]According to this arrangement, when the laser light is irradiated
onto the image-recording layer of the optical disc based on the image
information, the reflectance is changed as the absorbance of the
image-recording layer is changed, and a visible image corresponding to
the image information can be formed. In this visible image forming
process, since the operation of the modulating unit for modulating the
recording data is inhibited at the time the information is recorded on
the recordable side, the image data are not modulated. Therefore, a
special data transmission structure is not required to form a visible
image corresponding to the image information, and the data transmission
structure used for recording information on the recordable side can be
employed also in the image formation.

[0122]The optical disc recording apparatus of another aspect is

(10) an optical disc recording apparatus that records information by
irradiating the recordable side of an optical disc with a laser light,
the recording apparatus comprising: an optical pickup that irradiates
laser light onto the optical disc; an irradiation position adjusting unit
that adjusts the position of irradiation of the laser light by the
optical pickup onto the optical disc; and an image formation control unit
that controls the optical pickup and the irradiation position adjusting
unit such that a visible image corresponding to image information is
formed on the image-recording layer of the optical disc when the optical
disc having the recordable side on one side and an image-recording layer
on the other side is set with the image-recording layer facing the
optical pickup. The image formation control unit controls the laser light
irradiated from the optical pickup according to the gradation degree
indicated in the image information.

[0123]According to this arrangement, when the laser light is irradiated
onto the image-recording layer of the optical disc based on the image
information, the reflectance is changed as the absorbance of the
image-recording layer is changed, and a visible image corresponding to
the image information can be formed. In the visible image forming
process, laser light control corresponding to the gradation of the
respective positions (coordinate locations) on the image-recording layer
indicated in the image data can be performed, and a visible image with
gradation can be formed.

[0124]The optical disc recording apparatus of another aspect is

(11) an optical disc recording apparatus that records information by
irradiating the recordable side of an optical disc with a laser light,
the recording apparatus comprising: a rotating unit that rotates the
optical disc; an optical pickup that irradiates laser light onto the
above side of the optical disc rotated by the rotating unit and is
movable along the radius diameter of the optical disc; and a laser level
control unit that controls the level of the laser light emitted from the
optical pickup upon formation of a visible image on the image-recording
layer, and controls the level of the laser light based on the image data
representing the visible image to be formed such that the laser level is
set at a first intensity that hardly changes the recording layer and the
image-recording layer of the optical disc or at a second intensity that
hardly changes the recording layer but changes the color of the
image-recording layer.

[0125]According to this arrangement, when an optical disc of the invention
is used, information recording can be conducted on the recording layer by
irradiation with laser light similarly to conventional information
recording, and, in addition, a visible image can be recorded on the
image-recording layer. Further, since both of the information recording
and the visible image formation can be conducted by irradiation of the
laser light onto the same side of the optical disc, it is not necessary
for users to do troublesome operations such as reversing and reloading of
the optical disc.

[0126]A method of forming an image according to the invention uses an
optical disc recording apparatus having an optical pickup that conducts
information recording by irradiating laser light onto the recordable side
of the optical disc. The method includes forming a visible image on the
image-recording layer provided on the side of the optical disc that is
opposite to the recordable side. The method includes controlling the
laser light emitted by the optical pickup such that a visible image
corresponding to image information is formed on the image-recording layer
of the optical disc while the irradiation position of the laser light
emitted by the optical pickup is moved along a predetermined spiral or
concentric path on the image-recording layer. In the method, unit areas
are defined by dividing the optical disc into some sector-shaped regions,
and each unit area is defined as the area containing the predetermined
number of the adjacent spiral or concentric paths in each region. The
irradiation timing of the laser light onto the paths in the unit area is
controlled to express the contrasting density of each unit area in the
visible image. As explained in the above, the image management
information of the image can be obtained by pre-pit signals from the
pre-pit signal area of the optical disc.

[0127]According to this method, when the laser light is emitted in
accordance with the administrative information of the image obtained by
detecting the pre-pit signal from the prepit signal area, the reflectance
of the image-recording layer can be changed as the absorbance of the
image-recording layer is changed, and a visible image can be formed in
accordance with the image information. In this visible image forming
process, the laser irradiation timing control can be performed in
accordance with the gradation level of each position (each coordinate
location) on the image-recording layer indicated in the image
information, and a visible image with gradation can be obtained.

[0128]It is preferable that, in the forming a visible image, the laser
wavelength is 630 nm to 680 nm and the numerical aperture is 0.6 to 0.7.
Using a pickup under such conditions, the same pickup as that for a
recordable DVD can be shared. Furthermore, recording can be carried out
while obtaining a tilt margin and a beam spot diameter that are suitable
for a substrate having a thickness of 0.3 mm to 0.9 mm, more preferably
0.5 mm to 0.7 mm, still more preferably 0.55 mm to 0.65 mm. When such a
pickup is used, it is preferable that the pickup has a constitution of a
general pickup for a DVD using astigmatic focus error detection for focus
servo system and using push-pull method, three beam method, etc. as
tracking method.

A. Specific Structures of the Optical Disc Recording Apparatuses

[0129]The optical disc recording apparatus emits a laser beam to irradiate
the recordable side of an optical disc to record information. The optical
disc recording apparatus has a function of not only recording information
to the recordable side, but also emitting the laser beam to irradiate the
image-recording layer on the side of the optical disc opposite to the
recordable side, and forming a visible image corresponding to the image
information. Such an optical disc recording apparatus can record a
visible image also on the information-recording layer for digital data
recording if the optical disc uses a specific dye.

Structures of Optical Disc Recording Apparatuses

[0130]FIG. 4 is a block diagram showing the configuration of an optical
disc recording apparatus. As is shown in FIG. 4, an optical disc
recording apparatus 100, which is connected to a host personal computer
(PC) 110, comprises: an optical pickup 10, a spindle motor 11, an RF
(Radio Frequency) amplifier 12, a servo circuit 13, a decoder 15, a
control unit 16, an encoder 17, a strategy circuit 18, a laser driver 19,
a laser power control circuit 20, a frequency generator 21, a stepping
motor 30, a motor driver 31, a motor controller 32, a PLL (Phase Locked
Loop) circuit 33, an FIFO (First In First Out) memory 34, a drive pulse
generator 35, and a buffer memory 36.

[0131]The spindle motor 11 rotates the optical disc D on which data is to
be recorded, and the servo circuit 13 controls the number of revolutions
of the optical disc D. Since recording the optical disc recording
apparatus 100 in this embodiment employs the CAV (Constant Angular
Velocity) method, the spindle motor 11 rotates at a predetermined angular
velocity instructed by the control unit 16.

[0132]The optical pickup 10 is a unit that emits a laser beam for
irradiating the optical disc D that is rotated by the spindle motor 11,
and its structure is shown in FIG. 5. As is shown in FIG. 5, the optical
pickup 10 includes: a laser diode 53 for emitting a laser beam B; a
diffraction grating 58; an optical system 55 for focusing the laser beam
B on the surface of the optical disc D; and a light-receiving element 56
for receiving a reflected beam.

[0133]In the optical pickup 10, the laser diode 53 receives a drive
current from the laser driver 19 (see FIG. 4), and emits the laser beam B
at an intensity consonant with the drive current. In the optical pickup
10, the laser beam B emitted by the laser diode 53 is split, by a
diffraction grating 58, into a primary beam, a preceding beam and a
succeeding beam, and these three beams pass through a polarized beam
splitter 59, a collimator lens 60, a 1/4 wavelength plate 61 and an
object lens 62 and are focused on the surface of the optical disc D. The
three laser beams are reflected by the face of the optical disc D and
again pass through the object lens 62, the 1/4 wavelength plate 61 and
the collimator lens 60, and are reflected by the polarized beam splitter
59. From there, the reflected beams are transmitted through a cylindrical
lens 63 to the light-receiving element 56, which receives the reflected
beams and outputs them as light reception signals to the RF amplifier 12
(see FIG. 4). Thereafter, the RF amplifier 12 transmits these signals to
the control unit 16 and the servo circuit 13.

[0134]The object lens 62 is held by a focus actuator 64 and a tracking
actuator 65 so that it can be moved in the light axial direction of the
laser beam B and in the direction of the diameter of the optical disc D.
In accordance with a focus error signal and a tracking error signal
supplied by the servo circuit 13 (see FIG. 4), the focus actuator 64 and
the tracking actuator 65 move the object lens 62 in the light axial
direction and in the direction of the radius of optical disc D. The servo
circuit 13 generates the focus error signal and the tracking error signal
based on the light reception signals transmitted by the light-receiving
element 56 through the RF amplifier 12, and moves the object lens 62, in
the manner described above, so that the focusing and tracking operations
can be performed.

[0135]The optical pickup 10 includes a front monitor diode (not shown),
and when the laser beam is emitted by the laser diode 53, the front
monitor diode receives the beam and generates a current that is
transmitted from the optical pickup 10 to the laser power control circuit
20 in FIG. 4.

[0136]The RF amplifier 12 amplifies an RF signal that is produced by EFM
(Eight to Fourteen Modulation) and is received from the optical pickup
10, and outputs the resultant RF signal to the servo circuit 13 and the
decoder 15. For reproduction, the decoder 15 performs EFM demodulation
for the EFM modulated RF signal received from the RF amplifier 12 and
generates reproduction data.

[0137]Transmitted to the servo circuit 13 is an instruction signal from
the control unit 16, an FG pulse signal from the frequency generator 21
that has a frequency consonant with the number of revolutions of the
spindle motor 11, and an RF signal from the RF amplifier 12. Based on
these signals, the servo circuit 13 rotates the spindle motor 11, and
conduct focusing or tracking control of the optical pickup 10. The method
used for driving the spindle motor 11 to record information on the
recordable side (information-recording layer) of the optical disc D or to
form a visible image on the image-recording layer (see FIGS. 1A and 1B)
of the optical disc D can be either a CAV (Constant Angular Velocity)
method of driving the optical disc D at a predetermined angular velocity,
or a CLV (Constant Linear Velocity) method of rotating the optical disc D
to obtain a predetermined linear velocity for recording. The optical disc
recording apparatus 100 explained by FIG. 4 and the like employs the CAV
method, and the servo circuit 13 rotates the spindle motor 11 at a
predetermined angular velocity designated by the control unit 16.

[0138]Stored in the buffer memory 36 is information (hereinafter referred
to as recording data) to be recorded on the recordable side of the
optical disc D and information (hereinafter referred to as image
information) corresponding to a visible image that is to be formed on the
image-recording layer of the optical disc D. The recording data stored in
the buffer memory 36 are output to the encoder 17, while the image
information is output to the control unit 16.

[0139]The encoder 17 performs EFM modulation on the recording data
received from the buffer memory 36, and outputs the obtained recording
data to the strategy circuit 18. The strategy circuit 18, for example,
performs a time axis correction process on the EFM signal received from
the encoder 17, and outputs the resultant EFM signal to the laser driver
19.

[0140]The laser driver 19, under the control of the laser power control
circuit 20, drives the laser diode 53 (see FIG. 5) of the optical pickup
10 in accordance with a signal which is received from the strategy
circuit 18 and which is modulated based on the recording data.

[0141]The laser power control circuit 20 controls the power for a laser
beam emitted by the laser diode 53 (see FIG. 5) of the optical pickup 10.
Specifically, the laser power control circuit 20 controls the laser
driver 19 such that the optical pickup 10 emits the laser beam at an
intensity that matches the optimum target value of the laser power
designated by the control unit 16. The laser power control conducted by
the laser power control circuit 20 is feedback control for the emission
of the laser beam at the target intensity by the optical pickup 10, using
the value of the current supplied by the front monitor diode of the
optical pickup 10.

[0142]The image information supplied by the host PC 110 and stored in the
buffer memory 36 are transmitted through the control unit 16 to the FIFO
memory 34 and are stored therein. In this case, the image information
stored in the FIFO memory 34, i.e., the image information supplied to the
optical disc recording apparatus 100 by the host PC 110, includes the
following information. The image information is used to form a visible
image on the face of the optical disc D, and as is shown in FIG. 6,
information representing a gradation level (density) is written for each
of n coordinate points (indicated by black dots) on each of multiple
concentric circles centered on the center O of the optical disc D. The
image information represents the gradation level for each of the
coordinate points, in order from the coordinate points P11, P12, . . .
and P1n, belonging to the innermost circle, to coordinate points P21,
P22, . . . and P2n, belonging to the externally adjacent circle, to the
coordinate points along the externally adjacent circle and up to
coordinate points Pmn on the outermost circle. The data representing the
gradation levels of the coordinate points along the polar coordinate are
transmitted to the FIFO memory 34 in the above order. It should be noted
that FIG. 6 is a schematic diagram for clearly showing the positional
relationships of the coordinates, and the actual coordinate points are
disposed at a higher density. When the host PC 110 employs a
commonly-used bit-map format to prepare image information to be formed on
the image-recording layer of the optical disc D, the host PC 110 need
only convert the bit map data into the polar coordinate data described
above and transmit the obtained image information to the optical disc
recording apparatus 100.

[0143]To form a visible image on the image-recording layer of the optical
disc D based on the thus received image information, the PLL circuit 33
transmits an image recording clock signal to the FIFO memory 34. Every
time the FIFO memory 34 receives the clock pulse of the image recording
clock signal, the piece of information representing the gradation level
of a coordinate point stored before any other pieces of information
representing the gradation level is output by the FIFO memory 34 to the
drive pulse generator 35.

[0144]The drive pulse generator 35 generates a drive pulse to control the
timing at which a laser beam is to be emitted by the optical pickup 10.
The drive pulse generator 35 generates a drive pulse having a pulse width
consonant with information which is read from the FIFO memory 34 and
which represents a gradation level for each coordinate point. For
example, when the gradation level of a specific coordinate point is
comparatively high (the density is high), as is shown in FIG. 7A, the
drive pulse generator 35 generates a drive pulse having an extended pulse
width with respect to a write level (the second intensity). When the
gradation level is comparatively low, as is shown in FIG. 7B, the drive
pulse generator 35 generates a drive pulse having a reduced pulse width
of the write level. The write level is such a power level that when the
laser beam at this level is emitted and irradiated to the image-recording
layer of the optical disc D, the reflectance of the image-recording layer
is clearly changed. And when the above described drive pulse is
transmitted to the laser driver 19, for a period corresponding to the
pulse width, the laser beam at the write level is emitted by the optical
pickup 10. Therefore, when the gradation level is high, the laser beam at
the write level is emitted longer, and the reflectance of a larger region
in the unit area on the image-recording layer of the optical disc D is
changed. As a result, the user visually recognizes that the area is an
area having a high density. In this embodiment, the length of the region
in the unit area (the unit length) whose reflectance is to be changed is
varied, so that the gradation contained in the image information is
expressed. The servo level (the first intensity) is such a power level
that the image-recording layer of the optical disc D is substantially
unchanged when irradiated by the laser at the power of this level. To a
region whose reflectance need not be changed, the laser beam at this
servo level should be emitted instead of the laser beam at the write
level.

[0145]As described above, the drive pulse generator 35 generates a drive
pulse that is consonant with information representing the gradation level
for each coordinate point. In addition, the drive pulse generator 35
inserts a very short pulse at the write level or a pulse at the servo
level regardless of the information representing the gradation level when
required for the power control by the laser power control circuit 20 or
the focusing and the tracking control by the servo circuit 13. For
example, when, as is shown in FIG. 8A, a laser beam at the write level
has to be emitted for a period T1 in order to express a visible image in
accordance with the gradation level at specific coordinates contained in
the image information and the period T1 is longer than a predetermined
servo cycle ST for controlling the laser power, a servo off-pulse (SSP1)
having a very short period t is inserted at the end of the servo cycle
ST. When, as is shown in FIG. 8B, a laser beam at the servo level has to
be emitted for a period equal to or longer than the servo cycle ST in
order to express a visible image in accordance with the gradation level
at specific coordinates contained in the image information, a servo
on-pulse (SSP2) is inserted at the end of the servo cycle ST.

[0146]As is described above, the laser power control circuit 20 controls
the laser power based on the current (which has a value corresponding to
the intensity of the emitted laser beam) supplied by the front monitor
diode 53a that receives the laser beam emitted by the laser diode 53 (see
FIG. 5) of the optical pickup 10. More specifically, as is shown in FIG.
9, the laser power control circuit 20 performs sample holding of the
value that corresponds to the intensity of the laser beam received by the
front monitor diode 53a (S201 and S202). Then, when the laser beam is
emitted at the write level as a target value, i.e., when a drive pulse at
the write level (see FIGS. 7A and 7B and FIGS. 8A and 8B) is generated,
the laser power control circuit 20 controls the laser power based on the
sample holding results so as to emit the laser beam at the target write
level transmitted by the control unit 16 (S203). Further, when a laser
beam is emitted at the servo level as a target value, i.e. when the drive
pulse at the servo level (see FIGS. 7A and 7B and FIGS. 8A and 8B) is
generated, the laser power control circuit 20 controls the laser power
based on the sample holding results so as to emit the laser beam at the
target servo level transmitted by the control unit 16 (S204). Therefore,
when the drive pulse at the write level or the servo level is not output
continuously for a period longer than the predetermined servo cycle
(sample cycle) ST, the servo off-pulse SSP1 or the servo on-pulse SSP2 is
forcibly inserted regardless of the contents of the image information,
and the laser power control can be conducted for each level in the above
described manner.

[0147]The servo off-pulse SSP1 is inserted not only to control the laser
power, but also for the focusing or the tracking control performed by the
servo circuit 13. That is, the tracking control and the focusing control
are performed based on the RF signal received by the light-receiving
element 56 (see FIG. 5) of the optical pickup 10, i.e., the light
(reflected light) of the laser beam that is emitted by the laser diode 53
and returned from the optical disc D. In FIG. 10 an example signal is
shown which is received by the light-receiving element 56 upon
irradiation with the laser beam. As is shown in FIG. 10, the reflected
light at irradiation with the laser beam at the write level includes peak
portion K1 at the rising time for the laser beam and subsequent shoulder
portion K2 in which the laser level is constant, and the shaded area is
regarded as the energy used for image formation. The energy used for
image formation is not always a constant value, and may vary depending on
the situation. Therefore, it is anticipated that the shape of the shaded
area varies each time. That is, the reflected light of a laser beam at
the write level carries a lot of noise and stable reflected light is not
always obtained. When this reflected light is employed, it will interfere
with accurate focusing and tracking control. Therefore, as described
above, when a laser beam at the write level is continuously emitted for a
long period of time, the reflected light of a laser beam at the servo
level can not be obtained, and the focusing control and the tracking
control can not be correctly performed.

[0148]This is why the servo off-pulse SSP1 is inserted so that the
reflected light of a laser beam at the servo level can be obtained
periodically and so that the focusing control and the tracking control
are preformed based on the obtained reflected light. To form a visible
image on the image-recording layer of the optical disc D, unlike the
recording of information on the recordable side, tracing along the
pregroove (guide groove) that is formed in advance on the optical disc D
need not be performed. Therefore, in this embodiment, the target value
for the tracking control is set as a fixed value (a predetermined offset
value).

[0149]This control method can be employed not only for forming image
information on the image-recording layer, but also for forming image
information on the recordable side. That is, when a material whose
reflectivity and color can be changed by irradiation with a laser beam is
employed for the recordable side (information recording layer), an image
can be formed on the recordable side as well as on the image-recording
layer. However, when a visible image is formed on an area on the
recordable side, the original data recording can not be performed on the
area. Accordingly, it is preferable to separate the area for recording
data from the area for forming a visible image in advance.

[0150]It is also preferable to minimize the period required for inserting
the servo off-pulse SSP1 and the servo on-pulse SSP2 as long as various
servo controls, such as the laser power control, the tracking control and
the focusing control are not impaired. When the insertion period is very
short, the various servo controls can be conducted while hardly affecting
the visible image to be formed.

[0151]Referring again to FIG. 4, the PLL circuit (signal output unit) 33
multiplies the FG pulse signal at a frequency supplied by the frequency
generator 21 which is consonant with the revolution speed of the spindle
motor 11, and outputs a clock signal to be used for forming a visible
image, which will be described later. The frequency generator 21 employs
a counter-electromotive current obtained by the motor driver of the
spindle motor 11 and outputs the FG pulse at a frequency consonant with
the number of spindle revolutions. For example, when, as is shown in the
upper portion in FIG. 11, the frequency generator 21 generates eight FG
pulses per one revolution of the spindle motor 11, i.e., per one
revolution of the optical disc D, the PLL circuit 33 outputs a clock
signal having a frequency equivalent to a multiple of the FG pulse (for
example, a frequency equivalent to five times the FG pulse signals, or 40
pulses at level H during one revolution of the optical disc D), i.e.,
outputs a clock signal having a frequency that is consonant with the
speed at which the optical disc D is rotated by the spindle motor 11, as
is shown in the lower portion in FIG. 11. As a result, the clock signal
obtained by multiplying the FG pulse signal is output by the PLL circuit
33 to the FIFO memory 34, and for each cycle of the clock signal, i.e.,
for each rotation of the disc D by a specific angle, data representing
the gradation level at one coordinate point stored in the FIFO memory 34
is output to the drive pulse generator 35. The PLL circuit 33 may be
employed to generate a clock signal obtained by multiplying the FG pulse.
However, when a motor that has a satisfactorily stable driving capability
is employed, instead of the PLL circuit 33, a crystal oscillator may be
employed to generate the above described clock signal obtained by
multiplying the FG pulse, i.e., a clock signal having a frequency that is
consonant with the speed at which the optical disc D is revolve.

[0152]The stepping motor 30 is a motor for moving the optical pickup 10 in
the direction of the radius of the optical disc D that is loaded. The
motor driver 31 rotates the stepping motor 30 to a degree consonant with
the pulse signal supplied by the motor controller 32. In accordance with
a moving start instruction which is issued by the control unit 16 and
which includes the information about the direction and the distance of
the movement of the optical pickup 10 along the radius, the motor
controller 32 generates a corresponding pulse signal and outputs it to
the motor driver 31. When the stepping motor 30 moves the optical pickup
10 in the direction of the radius of the optical disc D and the spindle
motor 11 rotates the optical disc D, the laser irradiation position of
the optical pickup can be moved to various locations on the optical disc
D, and the above described components constitute irradiation position
adjustment unit.

[0153]The control unit 16 is constituted by a CPU (Central Processing
Unit), a ROM (Read Only Memory) and a RAM (Random Access Memory), and
controls the individual sections of the optical disc recording apparatus
100 in accordance with a program stored in the ROM, so that the recording
process on the recordable side of the optical disc D and the image
forming process on the image-recording layer of the optical disc D are
concentrically controlled.

[0154]The configuration of the optical disc recording apparatus 100 of
this embodiment is as described above.

B Operation of Optical Disc Recording Apparatus

[0155]The operation of the thus arranged optical disc recording apparatus
100 will now be described. As is described above, the optical disc
recording apparatus 100 can record, on the recordable side of the optical
disc D, information such as music data received from the host PC 110, and
can also form, on the image-recording layer of the optical disc D, a
visible image that corresponds to the image information supplied by the
host PC 110. While referring to FIGS. 12 and 13, an explanation will now
be given about the operation of the optical disc recording apparatus 100
that can perform data recording and visible image formation.

[0156]When the optical disc D is loaded into the optical disc recording
apparatus 100, first, the control unit 16 controls the optical pickup 10
and the like so as to determine what format the side of the optical disc
D facing the optical pickup 10 has. For example, in the case of a DVD-R,
the presence or absence of land pre-pit signals and pre-record signals is
detected, and in the case of a DVD+R, the presence or absence of ADIP
(Address in Pregroove) is detected (Step Sa1). When such information is
not recorded, the disc is not recognized as an optical disc.

[0157]For example, when land pre-pit signals or pre-record signals are
detected on a DVD-R as the loaded optical disc D, or when ADIP is
detected on a DVD+R as the loaded optical disc D, it is confirmed that
the optical disc D is set such that the recordable side faces the optical
pickup 10, and the control unit 16 conduct a control process of recording
the date supplied from the host PC 110 on the recordable side (Step Sa2).
Since the control process of recording the data is similar to that
employed in a conventional optical recording apparatus (such as a DVD-R
or DVD+R drive apparatus), description thereof is omitted.

[0158]On the other hand, when pre-pit signals representing an optical disc
capable of forming an image are detected from the loaded optical disc D,
it is confirmed that the optical disc D is set such that the
image-recording layer faces the optical pickup 10, and the control unit
16 determines whether it is possible to retrieve the disc ID of the
loaded optical disc D (Step Sa3). The disc ID of the optical disc D can
be included in the pre-pit signals. Further, for example as shown in FIG.
14, a visible image corresponding to the information obtained by coding
the disc ID may be recorded along the outermost circumference or the
innermost circumference (including the intermediate position between the
logo region and the image forming region) of the optical disc D on the
image-recording layer side. In FIG. 14, as is shown, the disc ID is
recorded on the image recording layer of the optical disc D by forming
reflective areas 301a and non-reflective areas 301b having lengths
respectively corresponding to the codes along the outermost
circumference. The control unit 16 traces the laser irradiation position
of the optical pickup 10 along the outermost circumference of the optical
disc D, and obtains the disc ID based on the reflected light.

[0159]Therefore, when the reflective regions 301a and the non-reflective
regions 301b that correspond to the disc ID are not formed in the
outermost-portion of the image-recording layer, it can be ascertained
that the optical disc D is an ordinary optical disc, such as a CD-R or
DVD-R, that does not have a image-recording layer. When, as in this case,
a disc ID can not be obtained, the control unit 16 ascertains that the
optical disc D is incapable of visible image formation (step Sa4), and
notifies a user of this determination.

[0160]When the disc ID can be obtained from the optical disc D, the
control unit 16 waits until an image forming instruction including the
image information is issued by the host PC 110 (step Sa5). When the image
forming instruction is issued, the control unit 16 performs an
initialization process in order to form a visible image on the
image-recording layer of the optical disc D (step Sa6). More
specifically, the control unit 16 permits the servo circuit 13 to rotate
the spindle motor 11 at a predetermined angular speed, or sends to the
motor controller 32 an instruction for moving the optical pickup 10 to
the initial innermost position along the radius of the optical disc D,
and permits the motor controller 32 to drive the stepping motor 30.

[0161]Furthermore, in the initialization process for image formation, the
control unit 16 gives instruction about the target focus control value to
the servo circuit 13, so that the image-recording layer of the optical
disc D is irradiated with a laser beam whose beam spot diameter is larger
than the beam spot diameter employed in the information recording on the
recordable side.

[0162]A more specific explanation will now be given about the focusing
control process performed when the above described target value is
designated. As is described above, the servo circuit 13 performs the
focusing control based on the signal output by the light-receiving
element 56 of the optical pickup 10. In the process of recording data on
the recordable side of the optical disc D, the servo circuit 13 drives
the focus actuator 64 (see FIG. 5) such that circular return light A in
FIG. 15 is received at the center of four areas 56a, 56b, 56c and 56d of
the light-receiving element 56 in FIG. 15. That is, when the amounts of
light received in the areas 56a, 56b, 56c and 56d are defined as a, b, c
and d, the focus actuator 64 is driven so that (a+c)-(b+d)=0 is
established.

[0163]For forming a visible image on the image-recording layer of the
optical disc D, the focusing control is performed such that the
image-recording layer is irradiated by the laser beam having a larger
diameter than the laser diameter employed during the information
recording on the recordable side. When the shape of the return light
received by the light-receiving element 56 in FIG. 15 is an ellipse (B or
C in FIG. 15), the servo circuit 13 drives the focus actuator 64 such
that this elliptical return light can be received by the light-receiving
element 56 because the spot of the laser beam B or C is larger than the
circular laser beam A. In other words, the focus actuator 64 is driven to
satisfy (a+c)-(b+d)=α (α is not 0). Therefore, in this
embodiment, the control unit 16 and the servo circuit 13 constitute beam
spot control unit.

[0164]As is described above, when the control unit 16 permits the servo
circuit 13 to set α (not 0) in the initialization process for
forming the visible image, the image-recording layer of the optical disc
D can be irradiated with the laser beam having a larger spot diameter
than that employed in the information recording on the recordable side.
Since the image-recording layer of the optical disc D is irradiated with
the laser beam of a larger spot diameter than that employed in the
information recording on the recordable side, the following effects can
be obtained. That is, in the embodiment, the laser beam is emitted for
forming a visible image while the optical disc D is rotated, similarly to
the information recording on the recordable side. Therefore, when the
diameter of the beam spot of the laser beam is increased, a visible image
can be formed on the entire image-recording layer of the optical disc D
within a shorter period of time. The reason for this will now be
described while referring to FIGS. 16A and 16B. In a comparison between
the case where the beam spot diameter BS is large and the case where the
beam spot diameter BS is small, the area subjected to visible image
formation upon one revolution of the optical disc D is larger when the
beam spot diameter BS is larger, as specifically shown in FIGS. 16A and
16B. Therefore, when the beam spot diameter BS is small, the optical disc
D must be rotated more to form a visible image on the entire area (in the
example in FIGS. 16A and 16B, six revolutions are required when the beam
spot diameter BS is small while four revolutions are required when the
beam spot diameter BS is large, and), so that an extended period of time
is required for image formation. For this reason, in the process for
forming a visible image, the optical disc recording apparatus 100 in this
embodiment emits the laser beam having a larger spot diameter than that
employed for information recording.

[0165]In the initialization process for image formation, the control unit
16 sends instructions about the target values for the write level and the
servo level to the laser power control circuit 20 such that the optical
pickup 10 emits the laser beam at the write level and the servo level
corresponding to the obtained disc ID. That is, the target values for the
write level and the servo level are stored in the ROM of the control unit
16 for each of a plurality of disc ID types. The control unit 16 reads
the target values for the write level and the servo level that correspond
to the obtained disc ID, and sends instructions about these target values
to the laser power control circuit 20.

[0166]Based on the following reasons, the target power values are set in
accordance with the disc ID. The characteristic of the dye used in the
image-recording layer may differ depending on the type of the optical
disc D, and when the characteristic differs, the characteristic for the
level of laser beam power required for changing the reflectance of the
image-recording layer differs accordingly. Therefore, even if
satisfactory change in the reflectance of the image-recording layer of a
certain optical disc D is achieved by a laser beam at a certain write
level, it does not necessarily mean that the laser beam at the write
level can change the reflectance of the image-recording layer of another
optical disc D. Therefore, in this embodiment, the target values for the
write level and the servo level are obtained for optical discs that
correspond to various disc IDs in advance through experiments. Then, the
obtained target values in relationship to the individual disc IDs are
stored in the ROM so that optical power control can be conducted in
accordance with the characteristics of the image-recording layer of
various optical discs D.

[0167]When the control unit 16 performs the above described
initialization, the process for forming a visible image on the
image-recording layer of the optical disc D is actually started. As is
shown in FIG. 13, first, the control unit 16 transmits to the FIFO memory
34 image information received from the host PC 110 via the buffer memory
36 (step Sa7). Then, the control unit 16 employs an FG pulse signal
received from the frequency generator 21 to determine whether a
predetermined reference position on the optical disc D that is rotated by
the spindle motor 11 has passed through the laser irradiation position of
the optical pickup 10 (step Sa8).

[0168]While referring to FIGS. 17 and 18, an explanation will now be given
about a method for detecting the predetermined reference position, and
for determining whether the laser irradiation position has passed the
reference position. As is shown in FIG. 17, the frequency generator 21
outputs a predetermined number of FG pulses (eight FG pulses in this
example) during one revolution of the spindle motor 11, i.e., during one
revolution of the optical disc D. Therefore, the control unit 16 outputs
one of the FG pulses received from the frequency generator 21 as a
reference position detection pulse in synchronization with the rising
time of a reference pulse. The control unit 16 thereafter generates a
reference position detection pulse signal in synchronization with the
rising timing of the pulse which is generated one revolution after the
last reference position detection pulse (eight pulses after the pulse
functioning as the last reference position detection pulse in this
example). Since the reference position detection pulse is generated, this
pulse generation timing can be identified as the timing at which the
laser irradiation position of the optical pickup 10 passes the reference
position of the optical disc D. Specifically, as is shown in FIG. 18, if
the laser irradiation position of the optical pickup 10 at the generation
of the first reference position detection pulse is a position on the
thick line (since the optical pickup 10 can be moved in the radius
direction, possible irradiation position is represented by a line). When
the reference position detection pulse is generated after one revolution,
the laser irradiation position of the optical pickup 10 is also on the
thick line. As is described above, the radial line on which the laser
irradiation position is located at the time of the generation of the
first reference position detection pulse is defined as a reference
position, and the control unit 16 can detect when the laser irradiation
position passes the reference position on the optical disc D based on the
reference position detection pulse signal generated each time the optical
disc D makes one revolution. The chained line in FIG. 18 describes an
example of trajectory of the laser irradiation position from the time one
reference position detection pulse is generated to the time the next
reference position detection pulse is generated.

[0169]When the control unit 16 detects that the laser irradiation position
passes the reference position of the optical disc D by the above method
after receiving the image forming instruction from the host PC 110, the
control unit 16 increases a variable R representing the number of
revolutions by one (step Sa9), and then determines whether the variable R
is an odd number (step Sa10).

[0170]In this case, when the controller detects that the laser irradiation
position passes the reference position for the first time after receiving
the image forming instruction, the following calculation is conducted:
R=0 (initial value)+1=1. Then, at step Sa10 it is found that the variable
R is an odd number. When it is found that the variable R is an odd
number, the control unit 16 permits the optical pickup 10 to irradiate
the image-recording layer of the optical disc D with the laser beam so as
to form a visible image (step Sa11). More specifically, after the
reference position detection pulse is received, the control unit 16
controls the respective sections such that image information stored in
the FIFO memory 34 are sequentially output in synchronization with a
clock signal output by the PLL circuit 33. Under the control of the
control unit 16, information stored in the FIFO memory 34 indicating the
gradation level for one coordinate point is output to the drive pulse
generator 35 upon receiving each clock pulse from the PLL circuit 33, as
is shown in FIG. 19. The drive pulse generator 35 generates a drive pulse
having a corresponding pulse width in accordance with the gradation level
indicated by the information, and outputs it to the laser driver 19. As a
result, the optical pickup 10 emits the laser beam at the write level to
irradiate the image-recording layer of the optical disc D only for a
period corresponding to the gradation level of each coordinate point.
Since the reflectance of the irradiated area is changed, a visible image
as shown in FIG. 20 can be formed.

[0171]As is schematically shown in the Fig, the laser irradiation position
of the optical pickup 10 is moved along a circle a distance corresponding
to the regions indicated by C in FIG. 20 during one clock signal cycle (a
period from the leading edge of one pulse to the leading edge of the next
pulse) since the optical disc D is rotated by the spindle motor 11. While
the laser irradiation position is passing the regions C, the period for
the irradiation with the laser beam at the write level is changed in
accordance with the gradation level, so that the areas whose reflectance
is changed can be different between the respective regions C in
accordance with different gradation levels. Since the period for the
irradiation with the laser beam at the write level at passing each region
C is adjusted in accordance with the gradation level of each coordinate
point, a visible image consonant with the image information can be formed
on the image-recording layer of the optical disc D.

[0172]When the control unit 16 has performed the above irradiation process
for forming a visible image by using the laser beam that is controlled in
accordance with the image information, the process in the control unit 16
is returned to step Sa7 and image information supplied from the buffer
memory 36 are transmitted to the FIFO memory 34. Then, the control unit
16 determines whether the laser irradiation position of the optical disc
D has passed the reference position on the optical disc D. When the
control unit 16 confirms that the laser irradiation position has passed
the reference position, it increases the variable R by one. When the
resultant variable R is an even number, the control unit 16 controls the
individual sections so as to stop the visible image formation by the
irradiation of the optical disc D with laser beam (step Sa12). More
specifically, the control unit 16 prevents the transfer of the
information indicating the gradation level of each coordinate point from
the FIFO memory 34 to the drive pulse generator 35 in synchronization
with a clock signal received from the PLL circuit 33. That is, in the
next revolution of the optical disc D after the visible image is formed
with the laser beam at the write level, the control unit 16 halts the
irradiation with the laser beam for changing the reflectance of the
image-recording layer.

[0173]When the control unit 16 has halted the laser beam irradiation for
visible image formation, the control unit 16 instructs the motor
controller 32 to move the optical pickup 10 a predetermined distance
toward the outer edge in the direction of the radius (step Sa13). Upon
receiving this instruction, the motor controller 32 drives the stepping
motor 30 via the motor driver 31, and the optical pickup 10 is moved the
predetermined distance toward the outer edge.

[0174]As is described above, the predetermined distance the optical pickup
10 is moved in the direction of the radius on the optical disc D can be
appropriately determined in accordance with the beam spot diameter BS
(see FIGS. 16A and 16B) of the laser beam emitted by the optical pickup
10. That is, to form a high-quality visible image on the image-recording
layer of the optical disc D, it is necessary for the laser irradiation
position of the optical pickup 10 to be moved such that the laser
irradiation position can cover any area on the surface of the optical
disc D. Therefore, when the length of the travel distance unit of the
optical pickup 10 in the direction of the radius is defined as
substantially the same as the beam spot diameter BS of the laser beam
employed to irradiate the optical disc D, the laser beam can be emitted
to any area on the surface of the optical disc D, and an image having a
higher quality can be formed. Due to various factors such as the property
of the image-recording layer, a region larger than the beam spot diameter
of the emitted laser may be colored. In this case, the travel distance
unit should be determined so as to prevent overlap between adjacent
colored regions, taking into account the width of the colored regions. In
this embodiment, since the beam spot diameter BS is larger (e.g., about
20 μm) than the beam spot diameter employed for recording information
on the recordable side, the control unit 16 permits the motor controller
32 to drive the stepping motor 30 so as to move the optical pickup 10 in
the direction of the radius a distance substantially equivalent to the
beam spot diameter BS. It should be noted that a recent stepping motor 30
employs the μ step technique to adjust the travel distance at a 10
μm level. Thus, it is naturally possible to move the optical pickup 10
at a 20 μm order in the direction of the radius using the stepping
motor 30.

[0175]After the optical pickup 10 is moved a predetermined distance in the
direction of the radius, in order to change the target write level of the
laser value, the control unit 16 instructs the laser power control
circuit 20 to use the updated write level for the emission of the laser
beam (step Sa14). In this embodiment, the method used to form a visible
image is the CAV method in which the laser beam is emitted while the
optical disc D is rotated at a constant angular speed. When the optical
pickup 10 is moved toward the outer edge in the above described manner,
the linear velocity is increased. Therefore, when the optical pickup 10
is moved in the direction of the radius (toward the outer edge), the
target write level value is increased to such a laser power that the
reflectance of the image-recording layer of the optical disc D can be
sufficiently changed even when linear velocity is changed.

[0176]After the optical pickup 10 is moved in the direction of the radius
and the target write level is changed, the control unit 16 determines
whether there are any unprocessed image information for visible image
formation, i.e., whether there are image information that have not been
transmitted to the drive pulse generator 35 yet. When no such image
information is present, the processing is terminated (step Sa15).

[0177]When there is unprocessed image information that have not been
transmitted to the motor controller 32 yet, program control returns to
step Sa7, and the process for forming a visible image is repeated.
Specifically, the control unit 16 transmits image information to the FIFO
memory 34 (step Sa7) and determines whether the laser irradiation
position has passed the reference position on the optical disc D (step
Sa8). When the laser irradiation position has passed the reference
position, the control unit 16 increases, by one, the variable R
indicating the number of revolutions (step Sa9), and determines whether
the updated variable R is an odd number (step Sa10). When the variable R
is an odd number, the control unit 16 controls the individual sections to
emit the laser beam to form a visible image. And when the variable R is
an even number, the control unit 16 halts the laser emission for the
formation of a visible image (while emitting the laser beam at the servo
level), and performs the control processes, such as movement of the
optical pickup 10 in the direction of the radius and the updating of the
target write level value. That is, when the laser beam (including the
laser beam at a write level) for image formation is emitted and used to
irradiate the optical disc D during a certain revolution, the control
unit 16 halts the laser irradiation used for image forming during the
next revolution, and instead, moves the optical pickup 10 in the
direction of the radius. Since the moving of the optical pickup 10 and
the changing of the target write level are performed during the
revolution in which the image formation is not performed, image forming
is halted while the irradiation position and the power value of the laser
beam are changed, and the laser irradiation for image formation can be
started after the irradiation position and the intensity of the laser
beam are settled. Therefore, deterioration of the quality of the visible
image due to the travel of the optical pickup 10 in the direction of the
radius can be prevented.

[0178]The primary operation of the optical disc recording apparatus 100 of
this embodiment has been explained. According to the optical disc
recording apparatus 100, the laser beam is emitted and used for
irradiating the image-recording layer provided on the optical disc D to
form a visible image in accordance with the image information without
using additional printing unit while the individual sections of the
optical pickup 10 for recording information on the recordable side are
utilized as far as possible.

[0179]Furthermore, in this embodiment, the laser irradiation timing is
controlled based on the clock signal generated using an FG pulse produced
in accordance with the rotation of the spindle motor 11, i.e., the clock
signal generated in accordance with the number of revolutions of the
optical disc D. Therefore, the optical disc recording apparatus 100 can
obtain the laser irradiation position without requiring positional
information of the optical disc D. Thus, the optical disc recording
apparatus 100 does not require a specially manufactured optical disc D
having a pregroove (a guide groove) provided on the image-recording
layer, and a visible image consonant with image information can be formed
on the image-recording layer not having a preformed pregroove or
positional information.

[0180]Next, the recording of information (digital information) on the
information-recording layer is described. When an optical disc whose
information-recording layer is of dye-type is used, the unrecorded
optical disc is irradiated with laser light from the laser pickup while
being rotated at a predetermined linear recording velocity. The dye in
the information-recording layer absorbs the laser light to locally
increase its temperature, whereby the desired pits are formed to change
the optical characteristics in the pit region, thereby recording
information.

[0181]The waveform of the recording laser light for one pit may be a pulse
string or a single pulse. The proportion of the pulse(s) to the length
(pit length) on which information is to be actually recorded is
important.

[0182]The pulse width of the laser light is preferably 20 to 95% of the
length on which information is to be actually recorded, more preferably
30 to 90%, still more preferably 35 to 85%. When the recording waveform
is a pulse string, the total sum of the pulse widths is preferably in the
above range.

[0183]The power of the laser light depends on the linear recording
velocity. When the linear recording velocity is 3.5 m/s, the power of the
laser light is preferably 1 to 100 mW, more preferably 3 to 50 mW, still
more preferably 5 to 20 mW When the linear recording velocity is doubled,
the above suitable ranges of the power of the laser light are
respectively increased 21/2-fold.

[0184]The NA of the objective lens used for the pickup is preferably 0.55
or higher, more preferably 0.60 or higher, so as to improve the recording
density.

[0185]In the invention, a semiconductor laser having an oscillation
wavelength of 350 to 850 nm may be used as a recording light source.

[0186]When the information-recording layer is a phase change
information-recording layer, the information-recording layer comprises a
substance such as described above, and the phase transition between the
crystal phase and the amorphous phase can be repeated by irradiation with
laser light.

[0187]Upon recording of information, the phase change recording layer is
irradiated with a focused laser light pulse for a short time to melt the
phase change recording layer partially. The melted portion is rapidly
cooled by heat diffusion to solidify, thereby forming a recording mark in
the amorphous state. Upon erasing the information, the recording mark
portion is irradiated with laser light to be heated to a temperature
which is in the range of from the crystallization temperature of the
information-recording layer to the melting point of the
information-recording layer inclusive, and then slowly cooled to
crystallize the recording mark in the amorphous state, thereby returning
the recording mark portion to the initial unrecorded state.

[0188]According to the optical disc of the invention, a side on which
image formation can be carried out is readily distinguished from a side
on which image formation is not to be carried out, and quality control
can be facilitated. Furthermore, the image forming method of the
invention is suitable for image forming on such an optical disc.

[0189]Hereinafter, exemplary embodiments of the invention will be
described. However, the invention is not limited to these exemplary
embodiments.

[0190]Namely, according to an aspect of the invention, there is provided
an optical disc on which a visible image can be formed by irradiation of
laser light, which comprises a logo area on which visible information is
indicated, a pre-pit signal area, and an image forming area on which a
visible image can be formed by irradiation of laser light.

[0191]In the optical disc of an aspect of the invention, it is preferable
that the image forming area is positioned at a deeper level than the logo
area. It is preferable that the pre-pit signal area is positioned at a
deeper level than the logo area. It is preferable that an outer
circumference of the logo area is positioned closer to an outer
circumference of the optical disc than an inner circumference of the
pre-pit signal area. It is preferable that an image-recording layer of
the image forming area is formed between two substrates facing each
other. It is preferable that the two substrates each have a thickness of
0.3 mm to 0.9 mm. Furthermore, it is preferable that an indented portion
is formed on the substrate on which the image-recording layer is formed,
at the side having the image-recording layer, and the indented portion
forms a logo area. The logo area preferably comprises two or more layers.

[0192]According to another aspect of the invention, there is provided an
image forming method of forming a visible image by irradiation of laser
light on an optical disc, the method comprising detecting a pre-pit
signal from a pre-pit signal area formed on the optical disc, and forming
the visible image based on the result of the detection, wherein the
optical disc is the optical disc according to an aspect of the invention.
It is preferable that, in the forming of the visible image, the laser
wavelength is 630 to 680 nm and the numerical aperture is 0.6 to 0.7.

[0193]The foregoing description of the embodiments of the present
invention has been provided for the purposes of illustration and
description. It is not intended to be exhaustive or to limit the
invention to the precise forms disclosed. Obviously, many modifications
and variations will be apparent to practitioners skilled in the art. The
embodiments were chosen and described in order to best explain the
principles of the invention and its practical applications, thereby
enabling others skilled in the art to understand the invention for
various embodiments and with the various modifications as are suited to
the particular use contemplated. It is intended that the scope of the
invention be defined by the following claims and their equivalents.

[0194]The disclosure of Japanese patent Application No. 2005-2888847 is
incorporated herein by reference in its entirety.

[0195]All publications, patent applications, and technical standards
mentioned in this specification are herein incorporated by reference to
the same extent as if each individual publication, patent application, or
technical standard was specifically and individually indicated to be
incorporated by reference.